1. Field of the Invention
The present invention relates to a transfer feeder including a plurality of workstations to be used for a transfer press, and more specifically, to a transfer feeder to be used for a transfer press including a slide drive unit at each of the plurality of workstations.
2. Description of the Related Art
Hitherto, the transfer press provided with a plurality of workstations in the press body comprises a transfer feeder adapted to transfer a workpiece sequentially to each workstation.
Such a transfer feeder comprises a pair of parallel transfer bars disposed on both sides along the workpiece conveying direction, and each transfer bar is extending continuously through the entire length of all the workstations.
The workpiece machined at each workstation is held by workpiece holder provided between the pair of transfer bars, and conveyed to the next process while being lifted by the same amount. Therefore, the die height in the transfer press and the height of the conveying surface at the lower die are kept almost constant at each workstation for ensuring holding of the workpieces by the workpiece holder and preventing interference with the die at the time of carrying in and out each station.
The transfer bars may be driven by a main motor for slide driving via a complex link mechanism or a cam mechanism or, in recent years, driven by a specific servomotor provided separately from the main motor.
However, in the conventional transfer feeder, when driving the transfer bars by the main motor, loss of energy may be occurred at the link mechanism and the cam mechanism between the main motor and the transfer bars. In addition, since the transfer bars to be driven are long and large scaled, the main motor is obliged to be upsized. As a consequent, consumption of electric power increases, and thus it is economically disadvantageous.
Even in the case of employing a servomotor, in order to drive a long and large scaled transfer feeders reliably with a single servomotor, the upsized servomotor is necessary, whereby consumption of electric power increases and thus it is economically disadvantageous.
In addition, since various restrictions due to the movement of the transfer bars such that interference with the transfer bars must be eliminated through the processes for example are imposed on the die used in the transfer press, there are problems in that design freedom is low and much time and efforts are required for its design.
Accordingly, it is an object of the invention to provide a transfer feeder in which energy consumption at the driving mechanism can be saved, and the die for the transfer press can easily be designed.
Accordingly, the present invention is a transfer feeder to be used for a transfer press provided with a plurality of workstations comprising: a pair of parallel lift beams disposed along the workpiece conveying direction; another pair of lift beams disposed adjacent to the pair of lift beams on the upstream side or the downstream side as seen in the workpiece conveying direction so that the adjacent portion is located at the substantially center of the workstation in the workpiece conveying direction; lift driving mechanism for moving the pair of lift beams and another pair of lift beams independently in the vertical direction; a carrier provided for each lift beam; carrier driving mechanism provided with a linear motor for moving the carrier along the length of the lift beam; workpiece holder disposed between the pair of carriers opposed with each other in the direction orthogonal to the workpiece conveying direction and being capable of holding the workpiece and moving along with the pair of carriers; and controller for driving the pair of lift beams and of the carriers between the workstations respectively simultaneously and/or individually independently by controlling the lift driving mechanism and the carrier driving mechanism.
In the invention thus constructed, short lift beams each having a length as short as a transfer bar divided into several pieces instead of the conventional transfer bars extending continuously through all the workstations, and the lift beams and the carriers provided on the respective lift beams are driven by the individual lift driving mechanism and the carrier driving mechanism. Therefore, because the length of the lift beam is shorter than that of the conventional transfer beam, the lift driving mechanism can be downsized. As a consequent, even when energy consumption in the carrier driving mechanism is taken into account, consumption of energy in the entire system may be reduced significantly in comparison with the case in which the conventional large scaled transfer bar is driven by a large sized main motor, or a large sized servomotor for driving the slide, thereby promoting energy saving.
In addition, by controlling the lift driving mechanism and the carrier driving mechanism according to the die used, the lift beams and the carriers provided between the workstations are not affected by the size or the shape of the die, and thus can be driven without interference with the die. Therefore, in the transfer press, restrictions imposed on the die as is in the related art are alleviated and thus design freedom of the die increases.
In the invention, a slide drive unit is provided at each of the plurality of workstations, and the controller (3) can be adapted to drive the lift beams and the carriers in the sections between the workstations and the slides in the workstations simultaneously and/or individually independently by controlling the lift driving mechanism, the carrier driving mechanism, and the slide drive unit.
In the invention thus constructed, since the slide drive unit is provided for each workstation and the slide drive unit is controlled by the controller, in addition to the case of driving the slides at the respective workstation simultaneously without phase difference as in the case of the original transfer press, by driving them simultaneously under the different conditions, or by driving them individually and independently, the transfer press may have capabilities of the original transfer press, capabilities of the tandem press, and capabilities of a single press altogether, so that it can be adapted to various works.
In this invention, the adjacent portions between the pair of lift beams and another pair of lift beams are preferably provided at each workstation of the transfer press.
In the invention thus constructed, since it is possible to produce optimal feeding motion for each section between adjacent workstations, the freedom of die construction increases significantly, and thus manufacture of the die is further facilitated. In addition, since the section between adjacent workstations must simply be considered when producing feeding motion, acceleration generated at the lift beam can be restrained to the required minimum extent, and thus the transfer feeder can follow the high-speed motion of the press in cooperation with weight reduction of the lift beam itself.
Since the lift beams being significantly shorter than the conventional transfer bar are used in all the sections between the adjacent workstations, the lift driving mechanism can further be downsized. Since the length of the lift beam, the number of carriers used, and the size, the number, and the like of the driving mechanism may be the same for every workstation, the kinds of the member used are not increased, and thus manufacture is facilitated.
In the invention, it is preferable that the end portions of the pair of lift beams and the end portions of another pair of lift beams face toward each other in the workpiece conveying direction at the adjacent portions between the pair of lift beams and another pair of lift beams.
In the invention thus constructed, since the width space between the parallel lift beams increases by arranging the lift beams in parallel and in alignment with each other along the workpiece conveying direction as a whole, a sufficient space can be established between the lift beam and the die, which further facilitates designing of the die.
In the invention, it is preferable that the end portions of the pair of lift beams and the end portions of another pair of lift beams face toward each other in the direction orthogonal to the workpiece conveying direction in plan view at the adjacent portions between the pair of lift beams and another pair of lift beams.
The two lift beams being adjacent along the workpiece conveying direction have their adjacent portions in the vicinity of the centers of the workstations. In order to convey the workpieces with these lift beams, it is necessary to move the workpiece holder correctly to the centers of the workstations in the workpiece conveying direction. However, in the invention, since the adjacent portions of the lift beams are faced toward each other in the direction orthogonal to the workpiece conveying direction in plan view, the workpiece holder of the respective lift beams may be pulled into the centers of the workstations without inter-collision by moving the carriers of the respective lift beams alternately toward the adjacent portions, thereby achieving preferable conveyance of workpieces.
In the invention, the carrier is preferably provided with a carrier-type offset unit for moving the workpiece holder in the workpiece conveying direction.
According to the invention in which two lift beams are adjacent in the workpiece conveying direction, since the carrier-type offset unit moves the workpiece holder further beyond the range of movement in association with the movement of the carrier, the workpiece holder are correctly placed to the centers of the workstations, so that the same effects as described above can be obtained.
In the invention, the workpiece holder is preferably attached on the crossbar which is laid between the carriers facing toward each other with the workstation interposed therebetween, and the crossbar is provided with a crossbar-type offset unit for moving the workpiece holder in the workpiece conveying direction. In such a case, by providing the crossbar-type offset unit on the crossbar, the same effects as described above can be obtained.
In the invention described above, the case in which a crossbar is laid between the carrier-type offset units provided on the carriers and a workpiece holder is attached on the crossbar is also included in the invention because the offset unit is provided on the carrier.